Roller mill

ABSTRACT

The roller mill is principally useful as a crushing device for geologic material. The main central shaft is power rotated and carries a plurality of spaced discs rotating therewith. Arms swingably mounted on the discs carry rotatable crushing rollers. The discs and crushing rollers are surrounded by a rotatable shell or drum. Drum speed is controlled by a hydraulic pump which incorporates flow control to limit drum speed. Geologic material, such as ore, is broken to a manageable size and is fed into one end of the drum. Airflow or waterflow controls material flow rate through the drum and the central shaft speed controls the fineness of grinding as the crushing rollers are centrifugally engaged on the geologic material against the inner drum surface.

United States Patent John G. Brandes FOREIGN PATENTS [72] Inventor 12160 Younadale A San Fernando. 121,206 12/1918 Great Britain .1 241/129 Calif. 91340 [21] Appl 808,856 Prunar ExaminerLester M. Sv v1ngle [22] Filed Man 20 1969 ASSISIGII! Examiner-Gary L. Sm1th [45] Patented Aug. 10,!971 Attorney-Allan M. Shap1ro [54] ROLLER MILL ABSTRACT: The roller mill is princinally useful as a crushing 8 Claims,3 Drawing Figs. dev1ce for geolog1c matenal. The mam central shaft 15 pottler 1 rotated and cames a plurahty of spaced dlSCS rotating [52] US. Cl. I 241/33, therewith Arms swingably mounted on the discs carry mtata,

24HIO'ZH/I16,241/118341/122 ble crushing rollers. The discs and crushing rollers are sur- [51] lnLCl B02c 15/08 rounded by a rotatable she" or drum. Drum Speed i [50] Field of Search 241/107, trolled by a hydraulic pump which incorporates flow comm] l l l 161-463, to limit drum speed. Geologic material, such as ore, is broken 63v to a manageable size and is fed into one end of the drum. Airflow or waterflow controls material flow rate through the [56] Rderencesemd drum and the central shaft speed controls the fineness of UNITED STATES PATENTS grinding as the crushing rollers are centrifugally engaged on 2,536,332 l/ 195i Vincent 241/ 1 17 X the geologic material against the inner drum surface.

l 44 a '--I 2 8 2 4 lo 52 9 rx 66 5 52 I 5 4 3o 38 5G I a I 1 56 I 8 -r= t H 1 9o 1H l: q! 54 ROLLER MILL BACKGROUND OF THE INVENTION the basic difficulty in that grinding action is accomplished by the tumbling of balls or rods with the material to be crushed as the drum rotates. In such circumstances, much of the impaction occurs between the balls and by the balls against the interior of the drum. This results in a considerable amount of wear on both the balls and the drum, which shortens life, as well as places iron particles in the stream of ground material. Furthermore, the rotative speed of such ball mills is limited because grinding action occurs as the balls and material to be ground cascade in the interior of the drum as the drum rotates, below the speed at which the material will be held against the walls by centrifugal force. Thus, a definite rotative limit is set upon the operation of such devices with the result that large equipment is required for a particular throughput and fineness of grind.

SUMMARY OF THE INVENTION In order to aid in the understanding of this invention, it can be stated in essentially summary from that it is directed to a roller mill. The roller mill comprises a rotatably mounted drum within which is a centrally located power shaft carrying a plurality of spaced discs rotatable therewith. Rollers are mounted upon the discs so that they can swing out against the drum under centrifugal force. Drum speed is limited by a drum-driven braking device.

Accordingly, it is an object of this invention to provide a roller mill for the grinding of geologic'materials and particularly ores. It is a further object to provide a roller mill which employs a rotatable drum which is rotated by the action of the grinding mechanism therein. It is still another object to provide drum-speed-limiting means comprising a pump driven by drum rotation together with flow control means for the pump. It is still another object of this invention to provide a roller mill having a central shaft which is adapted to be power driven and which effectively carries rollers thereon which are centrifugally extended so that geologic material is crushed between the rollers and the interior of the drum. It is another object of this invention to provide discs upon the powered central shaft, which discs inhibit geologic material flow axially through the drum so that all material passing through the drum must pass adjacent the interior surface thereof. It is still another object to swingably mount the crushing rollers in separating discs and to mount the separating discs upon the central powered shaft to provide an economical structure of long life. It is still another object to provide for easily replaceable crushing roller rims and drums so that the wear portions of the roller mill can be conveniently and economically renewed.

Still other objects, features and attendant advantages of the present invention, together with various modifications, will become apparent to those skilled in the art from a reading of the following detailed description of the preferred embodiment constructed in accordance therewith, taken in conjunction with the accompanying drawings wherein like numerals designate like parts in the several figures.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view, with parts broken away, of the roller mill of this invention.

FIG. 2 is a vertical transverse section taken generally along the line 2-2 of FIG. I.

FIG. 3 is an enlarged fragmentary section taken generally along the line 3-3 of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT The roller mill of this invention is generally indicated in the drawings at 10. The moving parts of the roller mill are mounted upon base 12. In view of the fact that the roller mill 10 has a small size, even with a substantial throughput capacity and a fine grinding ability, roller mill 10 can be built as a portable unit. Thus, base 12 is conveniently of such nature that the roller mill 10 can be mounted upon or form an integral part of a truck or trailer. On the other hand, the base 12 can be in the form of skids to permit the mill to be moved onto and off a conveyance. If desired, the power supply for furnishing power to the roller mill can also be mounted on base 12. As is seen in FIG. 2, the base is preferably made of hollow tube for maximum strength in a lightweight structure to enhance portability.

Standards 14 and 16 are mounted upon the base. A plurality of rollers 18 are mounted in these standards for the rotatable support of drum 20. A sufficient number of support rollers 18 are provided to adequately support drum 20 without excessive distortion. Standards 14 and 16 are preferably divided on a horizontal plane through the axis of the drum for convenient drum placement. Guide rails 22 and 44 are circumferentially secured to the drum and adjacent respective standards 14 and 16 to maintain axial position of the drum with respect to standards l4 and 16 as well as base 12.

Bearing posts 26 and 28 are mounted upon the frame and at their upper ends carry main shaft bearings substantially on the axis of drum 20. Mainshaft 30 is rotatably mounted in the bearings therein. As is seen in FIG. 1, the right hand of mainshaft 30 carries main drive pulley 32. Shaft 30, through pulley 32, is rotated by the main power source, which is preferably a conventional internal combustion engine.

The opposite end of mainshaft 30, outside of the bearing on bearing post 26, carries a suitable pulley, not shown, which is engaged by belt 34. Belt 34 engages upon pulley 36 which in turn is mounted on countershaft 38. The outer end of countershaft 38 carries a pulley for belt drive around which is engaged belt 40. The screw conveyor 42 is mounted in feed hopper 44. The screw conveyor carries a pulley engaged by belt 40 so that, upon rotation of mainshaft 30, screw conveyor 42 also rotates. However, in order to stop feed, when such is desired, countershaft 38 is mounted upon a bearing which is movable to slacken belt tension. Thus, mainshaft 30 can continue rotation without further material feed should the drum become overloaded, or at the end of a run. Screw conveyor 42 is preferably in the form of an open coil spring so that geologic materials of different sizes can be fed withoutjamming.

Coverplate 46 extends around the otherwise open inlet end of drum 20. Coverplate 46 is stationary and is mounted by bracket 48 which also supports feed hopper 44. An opening in coverplate 46 carries funnel 50 by which geologic material are fed from the outlet of conveyor 42 into drum 20.

Generally, outlet hood 52 surrounds the otherwise open outlet end of drum 20 and is stationarily mounted upon bearing post 28. Outlet hood 52 has a downwardly directed opening 54 from which the milled geologic materials are discharged.

Mainshaft 30 is preferably square between the hearings on post 26 and 28. Square configuration provides convenient mounting for structures which are driven by the shaft. A plurality of discs 56 are mounted on mainshaft 30. Each of the discs 56 has a central opening thereto, one side of which matingly engages halfway around the shaft. Clamp 58 is engaged around the other half of the shaft and is clamped todisc 56 to conveniently securely mount the disc on mainshaft 30 to rotate therewith and to prevent axial motion of the disc with respect to the shaft. Each of the discs is of such diameter as to substantially reach the inner surface of drum 20 so that geologic material moving axially in the .drum must move adjacent the interior surface thereof.

Each of the discs 56 carries at least one, and preferably two, of the grinding rollers 60. As is seen in FIG. 2, disc 56 has a peripheral edge opening 62 therethrough of such size as to fairly closely embrace the grinding rollers. The grinding rollers are mounted upon discs 56 in such a manner as to permit them to swing outward under centrifugal force when mainshaft 30 is rotated in a clockwise direction, when viewed as in FIG. 2. Roller mounting is accomplished by links 64 and 66 which are pivotally mounted upon pivot pin 68 secured to plate 56 adjacent the opening 62. Links 64 and 66 thus can swing freely with respect to disc 56. The other end of links 64 and 66 carries bearing pin or axle 70 upon which grinding roller 60 rotates. Thus, the grinding roller 60 can be swung centrifugally outward against the inner surface of drum as discs 56 are rotatably driven, and the grinding rollers can rotate upon their bearing shafts or axles 70 to permit rolling action between the grinding rollers and the inner surface of the drum.

As is seen in FIG. 1, successive discs 56 are positioned upon shaft so that the axially successive rollers are positioned 90 apart. Additionally, the rollers 60 on each disc are oppositely offset with respect to its disc 56 so that overlapping roller paths are obtained. Thus, there are no dead spots between roller paths.

As is seen in FIG. 3, the grinding rollers 60 are preferably formed of two parts. The inner or hub wheel 72 contains bearings 74 which permit the roller to rotate on bearing axle 70. Bearings 74 are preferably'sealed to prevent material being ground from entering the bearing to destroy its rotative effectiveness. Hub wheel 72 is preferably flanged so that it can conveniently carry annular rim 76 which actually engages in the grinding operation. Bolts through the facing flanges secure the rim upon the hub wheel to make for secure attachment and easy maintenance replacement.

It can be easily seen that, when geologic material is sent through the drum for crushing, the power input of the mainshaft 30 as applied to the material via the grinding rollers will tend to cause rotation of drum 20 in the same direction as revolution of rollers 60 about mainshaft 30, albeit opposite to the direction of rotation of rollers 60 about their bearing axles 70. Such drum rotation is desirable because of its materialfeeding characteristics, as well as its wear-equalization characteristics, as it assits the rollers in causing the material to be lifted up for distribution along the interior surface of the drum. However, rotation of drum 20 must be controlled. In the absence of such control, drum speed approaches the revolutionary speed of the rollers which, if permitted to become identical, theoretically would eliminate any counterrotational force on the rollers. Speed control of the rotation of drum 20 is accomplished by provision ofa sprocket 78 which is secured to and peripherally embraces the drum. Chain 80 engages the sprocket 78 and engages around sprocket 82 on the drive shaft of hydraulic pump 84. Hydraulic pump 84 is mounted upon base 12 and its hydraulic fluid reservoir 86 is mounted adjacent thereto. A sufficient quantity of hydraulic fluid is provided in the reservoir and the pump suction extends toward the bottom of the reservoir. Pump discharge line 88 is in turn directed into the reservoir. Hydraulic fluid flow control valve 90 is positioned in pump discharge line 88 between pump 84 and the reservoir. Valve 90 is preferably a needle valve, or the like, so that fluid flow can be finely controlled, it being clear that the hydraulic pressure load imposed on the pump 84, by valved restriction of the pumps output or discharge, determines the magnitude of reactive braking force applied to chain 80. By this means, rotative speed of drum 20 is controlled.

As an example of operation, geologic material, such as ore precrushed to /z-inch size or less, for example, is fed by the feed worm 42. The open coil feed worm does not choke up and provides an even feed. Water can be employed as a feed control medium and-as a medium to prevent excessive dust. However, instead of employing water, a vacuum fan can be connected to opening 54, together with a centrifugal cyclone dust separator. Mainshaft 30 is run at about 200 r.p.m., for example, which speed is sufflcient not only to centrifugally swing grinding rollers 60 outward toward contact with the inner surface of drum 20 but also to apply adequate centrifugal grinding force against the material. The geologic material is caught between the rollers and the drum so that crushing takes place. Drum rotation is controlled by adjustment of valve to about 1 or 2 r.p.m.

Roller mill 10 can be operated in such a way that no classification of milled output is required, for all material is milled to an adequate fineness. Thus, a subsequent classifierwith feedback of oversized particles is unnecessary although employable if desired. The fineness of grind of geological material can be controlled in one or a combination of several ways. The first way is to increase the speed of shaft 30. This both increases the number of passes of grinding rollers 60 upon the geologic material as it travels through the drum, and it increases the centrifugal loading of roller 60 against the drum. Both of these effects work toward a finer grind. The second fineness control is by the control of feed rate. With a decrease in material, waterflow or airflow, a longer residence time in the drum causes finer grinding. Another control results from reducing the reactive braking force so that the drum speed approaches the speed of revolution of the rollers 60 about the mainshaft 30, thus reducing the interface grinding action on the material between the drum and rollers. By these means, an economical roller mill of high efficiency is achieved in a small structure.

The invention having been described in its preferred embodiment, it is clear that it is susceptible to numerous modifications and embodiments within the ability of those skilled in the art and without the exercise of the inventive faculty.

What I claim is:

1. A roller mill for grinding geologic material, said roller mill comprising:

a frame;

a drum, said drum having an imperforate substantially cylindrical interior surface, said drum having an open inlet end and an open discharge end, said drum being rotatably mounted on said frame;

inlet end cover means mounted on said frame at one end of said drum to substantially cover the inlet end of said drum and to feed geologic material into the inlet end of said drum;

an outlet hood adjacent said drum at the outlet end thereof, said outlet hood receiving ground geologic material discharged out of the outlet end of said drum;

grinding rollers within said drum, each of said grinding rollers being mounted for free rotation on its own axle;

a main shaft rotatably mounted on said frame and extending at least part way through the interior of said drum;

means mounting said grinding roller axles on said main shaft so that said grinding rollers can engage the imperforate substantially cylindrical interior surface ofsaid drum and to be driven by roller engagement with the interior surface of the drum and geologic material thereon as said main shaft is rotated thus to cause drum rotation on its rotatable mounting by engagement by said grinding rollers; and

brake means connected to said drum for rotation by said drum, said brake means being responsive to the rotative speed of said drum for applying braking force to restrain drum rotation.

2. The roller mill of claim 1 wherein said brake means comprises:

a hydraulic pump;

a reservoir mounted in association with said pump so that said pump can withdraw hydraulic fluid from said reservoir and discharge hydraulic fluid back to said reservoir; and

hydraulic flow control means connected to said pump to control the flow of hydraulic fluid through said pump to control the rotative speed of said pump and of said drum.

3. The roller mill of claim 2 wherein said hydraulic flow control means is a selectively variable valve in output restriction relationship t aid pump for y ng the d on id pump,

4. A roller mill for grinding geologic material, said roller mill comprising:

a frame;

a drum. said drum having a substantially cylindrical imperforate interior surface, i r m ing ro ata ly mounted on said frame;

inlet end cover means mounted on said frame at one end of said drum to substantially cover the inlet end of said drum and to feed geologic material into the inlet end of said drum;

an outlet hood adjacent said drum at the outlet end thereof, said outlet hood receiving ground geologic material discharged out of the outlet end of said drum;

a main shaft rotatably mounted on said frame and extending at least part way through the interior of said drum;

a plurality of discs mounted on said main shaft to rotate with said main shaft, said discs lying substantially normal to the axis of said main shaft, said discs having no substantial unfilled openings therethrough and extending substantially to the interior surface of said drum so as to constrain axial movement of geologic material through said drum to adjacent the interior surface of said drum;

grinding rollers freely rotatably mounted upon grinding roller axles, said grinding roller axles being mounted upon said discs so that said grinding rollers can engage the interior surface of said drum and geologic material on said surface to be driven by powered rotation of said mainshaft.

5. The roller mill of claim 4 wherein there are peripheral edge openings in said discs and said grinding rollers lie in said openings- 6, The roller mill of claim 5 wherein each of said driving rollers is mounted upon its disc by means of pivotable links, one end of each of said links carrying a grinding roller axle and the other end of each of said links being pivotably mounted on said discs, said links being positioned so that said grinding rollers can swing outwardly against the interior surface of said drum.

7, The roller mill of claim 5 wherein said drum rotates upon rotation of said mainshaft by engagement upon said drum of said grinding rollers driven by aid mainshaft;

a hydraulic pump connected to said drum to rotate with said drum;

a hydraulic reservoir mounted in association with said hydraulic pump so that said hydraulic pump can withdraw hydraulic fluid from and discharge hydraulic fluid back to said hydraulic fluid reservoir; and

a selectively variable flow control valve connected to the hydraulic fluid outlet of said pump to control the rotative speed of said pump by varying the load thereon and thereby brakedly control the rotative speed of said drum.

8. The roller mill of claim 7 wherein said grinding rollers comprise:

hub wheels rotatably mounted on said links; and

rims detachably mounted on said hub wheels so that said rims can be replaced upon wear. 

1. A roller mill for grinding geologic material, said roller mill comprising: a frame; a drum, said drum having an imperforate substantially cylindrical interior surface, said drum having an open inlet end and an open discharge end, said drum being rotatably mounted on said frame; inlet end cover means mounted on said frame at one end of said drum to substantially cover the inlet end of said drum and to feed geologic materIal into the inlet end of said drum; an outlet hood adjacent said drum at the outlet end thereof, said outlet hood receiving ground geologic material discharged out of the outlet end of said drum; grinding rollers within said drum, each of said grinding rollers being mounted for free rotation on its own axle; a main shaft rotatably mounted on said frame and extending at least part way through the interior of said drum; means mounting said grinding roller axles on said main shaft so that said grinding rollers can engage the imperforate substantially cylindrical interior surface of said drum and to be driven by roller engagement with the interior surface of the drum and geologic material thereon as said main shaft is rotated thus to cause drum rotation on its rotatable mounting by engagement by said grinding rollers; and brake means connected to said drum for rotation by said drum, said brake means being responsive to the rotative speed of said drum for applying braking force to restrain drum rotation.
 2. The roller mill of claim 1 wherein said brake means comprises: a hydraulic pump; a reservoir mounted in association with said pump so that said pump can withdraw hydraulic fluid from said reservoir and discharge hydraulic fluid back to said reservoir; and hydraulic flow control means connected to said pump to control the flow of hydraulic fluid through said pump to control the rotative speed of said pump and of said drum.
 3. The roller mill of claim 2 wherein said hydraulic flow control means is a selectively variable valve in output restriction relationship to said pump for varying the load on said pump.
 4. A roller mill for grinding geologic material, said roller mill comprising: a frame; a drum, said drum having a substantially cylindrical imperforate interior surface, said drum being rotatably mounted on said frame; inlet end cover means mounted on said frame at one end of said drum to substantially cover the inlet end of said drum and to feed geologic material into the inlet end of said drum; an outlet hood adjacent said drum at the outlet end thereof, said outlet hood receiving ground geologic material discharged out of the outlet end of said drum; a main shaft rotatably mounted on said frame and extending at least part way through the interior of said drum; a plurality of discs mounted on said main shaft to rotate with said main shaft, said discs lying substantially normal to the axis of said main shaft, said discs having no substantial unfilled openings therethrough and extending substantially to the interior surface of said drum so as to constrain axial movement of geologic material through said drum to adjacent the interior surface of said drum; grinding rollers freely rotatably mounted upon grinding roller axles, said grinding roller axles being mounted upon said discs so that said grinding rollers can engage the interior surface of said drum and geologic material on said surface to be driven by powered rotation of said mainshaft.
 5. The roller mill of claim 4 wherein there are peripheral edge openings in said discs and said grinding rollers lie in said openings.
 6. The roller mill of claim 5 wherein each of said driving rollers is mounted upon its disc by means of pivotable links, one end of each of said links carrying a grinding roller axle and the other end of each of said links being pivotably mounted on said discs, said links being positioned so that said grinding rollers can swing outwardly against the interior surface of said drum.
 7. The roller mill of claim 5 wherein said drum rotates upon rotation of said mainshaft by engagement upon said drum of said grinding rollers driven by said mainshaft; a hydraulic pump connected to said drum to rotate with said drum; a hydraulic reservoir mounted in association with said hydraulic pump so that said hydraulic pump can withdraw hydraulic fluid from and discharge hydraulic fluid back to said hydraulic flUid reservoir; and a selectively variable flow control valve connected to the hydraulic fluid outlet of said pump to control the rotative speed of said pump by varying the load thereon and thereby brakedly control the rotative speed of said drum.
 8. The roller mill of claim 7 wherein said grinding rollers comprise: hub wheels rotatably mounted on said links; and rims detachably mounted on said hub wheels so that said rims can be replaced upon wear. 